Tetrabromindigo and process of making same.



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wrnnnnmneunn. on vonwmxnn, NEAR ELBERFELD AND ALFRED human. or tennnnrnnn, GERMANY. ASSIGNORS TO FARBENFABEIKEN VORM. FRIEDR. BAYER e co, on nnnnnnnnn. GERMANY. A coneonn'mou on GERMANY.

TETRABROMINDIGO AND No Drawing.

"lb all :iiom it may concern:

Specification of Letters Eatent.

Application filed September 15, 1903. Serial No. 453,164.

PROCESS OF MAKING SAME.

file and the new telraln'omoindigo which Be it known that we, \VILHELU llunu 1 separates is filtered oil, treated with -21 diund Amman l-lnunn, doctors of philosophy, chemists, citizens of the German Emplrc,

residing at Volnviukel. neur lllberfehl, and

I lilberlehl, Gern'mny, respectively, have'inartificial light.

vented new and useful \Iinprovcments in Tetrabronioiiuligo and Processes of lvlaking Some, of which the following-is a specification.

Our invention relates to the manufacture uml production of a new tetrabrorno substitution product of indigo. lb is obtained in a very simple manner and with a very good yield by treating at a moderate temperature 1n presence of concentrated sulfuric acid indigo with bromin.

' The new bromo derivative of indigo is a valuable (lyestuil. It forms vets by the usual methods in use for preparing indligo vats. These vets (lye unincrclented cotton grcenishblue shades remarkable for their clearness and festness.

The new tetrebromoindigo is (list-inguishewl from the tetrabromoindogoes of the old art by yielding more greenish shades, and this rlill'erence is especially striking in it is also more soluble in organic solvents and its leuco-ccrnpound is more soluble in elkalies. It is soluble in hot glacial acetic acid and; easily soluble in lint phenol ancl benzalclehycle with n blue color. By treetnienlrwith oxidizing agents, 1?; Iurnishes a. product from which 21 brornoisatm of the melting point of about 215 Cgmay he isoleteqi, while the product furnished by the oxidation of the tetrnbrornoincligces of the old art consists of n bromoisntin melting at about 248 C.

ln creler to illustrate the new process more fully the following examples are given, the parts being by weight Example 1: 10 parts of finely powdered indigo are gradually introduced while stirring into ports of concentrated sulfuric acid (6% Be.) which has to be cooled to prevent sulfonzition of the indigo. parts of hroinin are then added in such 2; manner that its addition takes about half an hour and the mixture while being vigorously stirred is slowly heated to C. After about h( s the mixture is poured into water containing. a small quantity of bisullute solution. of caustic alkali at 80 0., filtered again and washed with warm water, and dried.. It is u reddish-blue powder which is soluble in concentrated sulfuric aeio. with u greenishblue'color.

When treated with alkaline reducing agents, a. g. hydrosulfite and NaOH, the new tetrabroinoindigo yields a yellow vat containing the leuco-compound from which vat unmordanted cotton is dyed in greenishblue shzules.

ll; is not necessary to use in the above ex ample the theoretical amount of: bromin because the hydrogen bromicl, formed durin the reaction, is oxidized by the sulfuric aci and will supply the bromin necessary for the completion of the reaction. We can therefore carry out our process with a, can siderably smaller amount of bromin than theoretically calculated.

Example H: 10 parts oil finely powdered indigo are gradually introdueedwhile stirring into 250 parts of concentrated sulfuric acid (66 Be), which haste be cooled to prevent sulfonation of the indigo. 20 parts of bromin are then added in such a manner that its addition takes about half an hour and the mixture while being vigorously stirred is slowly heated to 45 C. After about 1:2 hours the mixture is poured into water containing a small quantity of bisulfite and the new tetrnbromoindigo which separates is filtered off, treated with a dilute solution of caustic alkali at (1., filtered. again, washed with warm water, and lried.

VF havefurther found that the brominetion of incligo can also bekarried out by,

using hyclrobroinic acid (HlSr) alone and we have found that even bromid of sodium or other broinids' can be employed directly in the presence of sulfuric acid. It is advisable to carry out the process in a closed yc'scl to avoid an evaporation of Bill.

The new dye can also be obtained by start ing instead of from i1 digo, from. bromoascertained the nature of our invention and V in what manner the same is to beperformed,

we declare that what We claim is v -1. The herein-described process for producing tetrabromoindigo, which process con-' sists in treating indigo substances with brominating agents and concentrated sulfuric acid in the'absence of watcr, substantially' as described. i v

2. The herein-described process for pro- ..ducing tetrabromoindigo, which process con- ..sists 1n treating indigo substances with sulfuric acid with a greenish-blue color; 3 soluble in hot glacial acetic acid and easily soluble in hot lienol and benzaldchydc with a blue color; lhrnishing by treatment with oxidizing agents a product from which a bromoisatin melting at 215 C. may be 25 isolated; and yielding by treatment with hydrosulfite and caustic soda lye a yellow vat, from which unmordanted cotton is dyed greenish-blue shades, substantially as dcscribed. 3C

In testimony whereof we have hereunto set our hands in the presence of two sub-. scribing witnesses.

\VILHELM BAUER. [1,. s. ALFRED HER-RE. [n s.

W itnesscs:

4 O'r'ro Komo,

WM. WASHINGTCF' BRUNSWICK. 

